We hear this question A LOT this time of year – from readers, family, and friends alike. So here’s the easy answer: Set it to what’s comfortable for you and your family!
BUT – comfort is a complicated and entrenched behavior that’s rarely rational. For example, my father-in-law’s cousin set her air conditioning at 65° F (18° C) in the summer so she would have to wear a sweater. In the winter, she set her heat to 80° F (27° C) so she could wear short sleeves.
Since this concept of comfort is very subjective, let’s instead look at the factors affecting yours and then examine how you can use them to help you reduce your energy costs. We want you to live brighter throughout the winter by helping you set your thermostat at the best temperature for you and your family.
So, you’re saying there’s not an easy answer to my question.
Not exactly. Our normal circadian rhythm and different hormones (such as stress) fluctuate your body temperature during the day. Consequently, staying comfortable is a moving goal post. For example, you might usually feel alert during the morning, but you may tend to feel a little bit colder or drowsy after lunch (known as the “post lunch dip”).
As the day winds down, your body temperature drops. When you go to sleep, your core body temperature lowers further and heat radiates from your extremities. A National Institute of Health study found the best sleep happens as the body reaches “thermoneutrality.” For example, if you sleep wearing pajamas and covered by one sheet, this happens on average at 60° to 66° F (16° to 19° C).
When it comes to daytime room temperature, a series of psychological experiments by the Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) showed that people have been socialized to believe that 72° F (22° C) is the optimum comfortable room temperature. In fact, the preferred temperature for comfort ranges from 68° to 76° F (20° to 24° C), depending on the time of year and the type of clothing worn. In one set of ASHRAE experiments, participants who did not know the room’s temperature said they were as comfortable at 68° F (20° C) as they were at 72°F (22° C).
Ummm… That’s hard science. I wanted an easier answer.
Fair point! In that case, it’s now time to experiment on your family. When everyone is home, secretly lower the thermostat setting for few hours every day. For example, drop it from 72° F (22° C) to 70° F (21° C). See how your family reacts and take notes.
A few days later, drop the temperature another degree or two for a few hours. Chances are you won’t get a noticeable reaction until it goes below 68°F (20° C). When you determine the minimum comfort level temperature for your family, use that.
And keep in mind – for every degree you lower the thermostat during winter, you’ll save between 1 and 3% off your heating bill.
But what about when we’re out of the house or asleep?
When everyone is gone for the day, there’s no good reason to keep your home heated to its comfort level. The same applies to night time when everyone is asleep. In both cases, you can set the thermostat lower, even down to 62° F (17° C). This makes it easier for your body to achieve thermoneutrality, and you’ll get a better night’s sleep.
Of course, having a programmable or smart thermostat makes these kind of regular adjustments easy to schedule and maintain automatically.
By the way — if you’ve heard that setting your thermostat to one temperature throughout the day reduces energy usage, Newton’s Law of Cooling proves otherwise.
What happens if my family STILL complains about the house being cold?
Well, apart from practicing thermostat adjustments, the big factor affecting your energy usage is how well insulated and air sealed your home is. The more insulation you have and the better sealed your home is, the longer it takes for your home to lose heat. Reducing cold drafts can lower your energy costs and prevent problems with mold.
Also make sure to monitor your home’s humidity. The US EPA recommends 25% to 40% in the winter. Not only does humid air hold more heat, but your family will have fewer sinus problems from overly dry air. Most programmable and smart thermostats will display the relative humidity at the push of a button.
You should also reverse the spin of your ceiling fans to spin clockwise during fall and winter to circulate warm air properly. You want your fans to draw cool air up from the center of the room and blow warm air down to circulate evenly around the room, which improves comfort. The breeze created moves warm air behind furniture and can help inhibit mold growth on poorly insulated exterior walls. This technique works best when fans are set to medium or slow speed.
Don’t forget to close the curtains over windows at night. Thermally-back window treatments not only insulate against heat loss through windows but they also restrict cold air moving across the glass and and cooing. Curtains and similar window treatments can reduce heat loss by 10%.
Those tips are great, but please answer my question directly – “What’s the best temperature for my thermostat in winter?”
- If you’re at home in the daytime, 72° F (22° C) is a good start, but aim for 68° F (20° C).
- If you’re not at home in the daytime, or you’re asleep at night, we feel 66° F (19° C) to 62° F (17° C) is best.
But as we said before, the best temperature for your thermostat in winter is the one that keeps your family happy, warm, and comfortable. Saving energy and lowering your energy bills might be nice, but you might not want to sacrifice family harmony to achieve them.